Topic Contents

Testosterone

Test Overview

A testosterone test checks the
level of this male hormone
(androgen) in the blood. Testosterone affects
sexual features and development. In men, it is made in large amounts by the
testicles. In both men and women, testosterone is made
in small amounts by the
adrenal glands, and in women, by the
ovaries.

The
pituitary gland controls the level of testosterone in
the body. When the testosterone level is low, the pituitary gland releases a
hormone called
luteinizing hormone (LH). This hormone tells the
testicles to make more testosterone.

Before
puberty, the testosterone level in boys is normally
low. Testosterone increases during puberty. This causes boys to develop a
deeper voice, get bigger muscles, make
sperm, and get facial and body hair. The level of
testosterone is the highest around age 40, then gradually becomes less in older
men.

In women, the ovaries account for half of the testosterone in
the body. Women have a much smaller amount of testosterone in their bodies
compared to men. But testosterone plays an important role throughout the body
in both men and women. It affects the brain, bone and muscle mass, fat
distribution, the vascular system, energy levels, genital tissues, and sexual
functioning.

Most of the testosterone in the blood is bound to a
protein called sex hormone binding globulin (SHBG). Testosterone that is not
bound ("free" testosterone) may be checked if a man or a woman is having sexual
problems. Free testosterone also may be tested
for a person who has a condition that can change SHBG levels, such as hyperthyroidism or some types of kidney diseases.

Total testosterone levels vary throughout the day. They are usually highest in the morning and lowest in the evening.

Why It Is Done

A
testosterone test is done to:

See why a man is having problems in fathering a child (infertility). A low amount of testosterone can lead to
low sperm counts.

Check a man's sexual problems. Having a low level of testosterone may
lower a man's sex drive or not allow him to have an erection (erectile dysfunction).

See whether a high level of testosterone is causing a boy younger
than age 10 to have early signs of puberty.

Find out why a woman is developing male features, such as
excessive facial and body hair (hirsutism) and a deep voice.

Find out why a woman is having irregular menstrual
periods.

See if testosterone-lowering medicines are working in a man with
advanced
prostate cancer.

How To Prepare

You do not need to do anything before
you have this test. Your doctor may want you to do a morning blood test because
testosterone levels are highest between 7 a.m. and 9 a.m.

How It Is Done

The health professional taking a sample
of blood will:

Wrap an elastic band around your upper arm to stop the flow of
blood. This makes the veins below the band larger so it is easier to put a
needle into the vein.

Clean the needle site with alcohol.

Put the needle into the vein. More than one needle stick may be
needed.

Attach a tube to the needle to fill it with blood.

Remove the band from your arm when enough blood is
collected.

Put a gauze pad or cotton ball over the needle site as the needle
is removed.

Put pressure to the site and then a bandage.

How It Feels

The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch.

Risks

There is very little chance of a problem from
having a blood sample taken from a vein.

You may get a small bruise at the site. You can lower the chance
of bruising by keeping pressure on the site for several minutes.

In rare cases, the vein may become swollen after the blood sample
is taken. This problem is called phlebitis. A warm compress can be used several
times a day to treat this.

Ongoing bleeding can be a problem for people with bleeding
disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can
make bleeding more likely. If you have bleeding or clotting problems, or if you
take blood-thinning medicine, tell your doctor before your blood sample is
taken.

Results

A
testosterone test checks the level of this male
hormone (androgen) in the blood.

Normal

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

The testosterone level for a postmenopausal woman is
about half the normal level for a healthy, nonpregnant woman. And a pregnant
woman will have 3 to 4 times the amount of testosterone compared to a healthy,
nonpregnant woman.

High values

In boys younger than 10, a high level of testosterone may mean
early (precocious) puberty, a tumor in the testicles, or an abnormal adrenal
gland.

In women, a high level of testosterone may be caused by cancer
of the ovaries or adrenal glands or by
polycystic ovary syndrome (PCOS). In rare cases, the part of the ovary that makes testosterone can become very sensitive to luteinizing hormone (LH), causing very high testosterone levels. This condition is called hyperthecosis.

Low values

In men or boys who have gone through puberty, a low level of
testosterone may be caused by a problem with the testicles, such as slow
development of, an injury to, or a lack of testicles. It can also be caused
from treatment with the female hormone
estrogen, a problem with the
pituitary gland, or many long-term (chronic)
illnesses.

A low testosterone level in men can also be caused by certain
inherited diseases (such as
Klinefelter syndrome or
Down syndrome), liver disease (cirrhosis), or treatment for cancer of the
prostate gland.

Long-term (chronic) alcohol use can cause a low testosterone
level.

In women, a low level of testosterone may be caused by an
underactive pituitary gland,
Addison's disease, loss of
ovary function through disease or surgery, and some
medicines (such as
corticosteroids or estrogen).

Being very overweight, having long-term (chronic) pain, or taking some pain medicines can lower the level of sex hormone binding globulin (SHBG). This also decreases total testosterone level.

What Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include:

A really high level of
LH and a low level of testosterone often means that the testicles or ovaries
are not working properly. This is the pattern seen in women after menopause when their ovaries stop working.

A low LH level and a really low or high testosterone
level may mean a problem with the pituitary gland.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use.